Micronutrients Part 1A Flashcards
what defines group 1 micronutrients?
bind to and control type 2 steroid hormone receptors
what are examples of group 1 micronutrients? and which ones DIRECTLY interact with type II receptors?
vitamin A, calcium, vitamin D, selenium, iodine, fluoride, phosphorous, vitamin K (only bioactive forms of vit A, vit D and iodine)
In summary, what is the purpose of iodine?
Makes T3, which regulates synthesis of proteins that control thyroid function and BMR
In summary, what is the purpose of vit A (hint: 3) ?
regulate night vision, epithelial differentiation, gene expression
In summary, what is the purpose of vitamin D?
converted to calcitriol, regulates calcium levels in the body
What are type II steroid hormone receptors?
found in the nucleus. respond to ligands such as thyroid hormone, retinoic acid, and calcitriol
how much iodine is in each gram of potassium iodide fortified salt?
0.03g iodine per g salt
Where is the most iodine in our body found and how much ~?
thyroid gland (70-80%)
iodide is immediately converted to its ionic form, I-. The uptake of I- into the blank is mediated by an blank system that uses blank symporter.
thyroid gland, active transport, Na+/I- (NIS)
iodine contributes to the production of both T3 and T4. The T4 produced is converted to T3 by 5’deiodinase. The micronutrient blank is required for this conversion.
selenium
a patient is suffering from hypothyroidism. which hormone will be tested in their blood?
T4. T4 is more abundant than T3 and has a longer half-life
A patient has low T3 and T4, however is getting enough iodine and selenium. What could be the issue?
there could be some problem with the hypothalamus/ pituitary gland to signal the production TSH, or an issue with the thyroid recognizing TSH
what hormone interacts with T3 to regulate metabolic rate and growth of tissues?
thyroid hormone receptor (THR)
Where is T4 converted to T3?
liver
once in the thyroid, what amino acid of which protein interacts with iodine? how? what is the product? where does it occur specifically?
tyrosine of the thyroglobulin (THG) protein, iodide radical interacts with the ring of tyrosine to form cross-linking tyrosine residues, products are T4 and T3, occurs specifically in the colloid of the thyroid
Which hormone promotes the following processes:
- lipolysis
- bone production
- increase in heart rate
- muscle contraction
- nutrient digestion
T3
Hypothyroidism is the over-production of blank in the thyroid caused by a significant deficiency in blank.
TSH, iodine
When a fetus in the womb is deficient in iodine, this can cause which disease? What are the symptoms?
Cretinism
- growth abnormalities
- intellectual disabilities
What are the major forms of Vit A in the body? (4)
Retinol, Retinal, Retinyl ester, Retinoic acid
What are carotenes? What is their role in human nutrition?
- Carotenes are precursors of vit A (provitamins)
- ex. beta-carotene
- founds in plants –> convert to bioactive form of vit A when consumed by animals
What is the function and composition of retinyl esters? How does it enter the intestinal mucosal cell (enterocyte)? What enzyme is involved? How is it packaged in the intestinal cell?
- REs are a safe form of vit A (stable)
- main purpose is storage (have no direct function in the body)
- RE = retinol + fatty acid
- Retinyl esterase cleaves the fatty acid
- Retinol enters the intestinal enterocyte via passive diffusion (incorporated into micelles)
- Retinal is converted back into RE
(if not being used, stored in the hepatic stellate cells, ie. liver cells) - RE is then packaged into chylomicrons
What are the two fates of B-carotene once it enters the intestinal enterocyte? What is this dependent on?
- converted into retinal via the 15-15’-DO enzyme
- converted into retinol
- directly packaged into chylomicrons and sent to the liver
- packaged in VLDL then stored in adipose tissue
- cause hypercarotenosis (orange skin)
–> Depends on Vit A status of the person
- if deficient, B-carotene will be converted to vit A
What is the fate of RE once packaged into chylomicrons?
- transported to the liver
- converted to retinol (via retinyl esterase)
- retinol + retinol-binding protein (RBP) = retinol-RBP
What is the function of RBP? What does its synthesis depend on?
- RBP is used to transport retinol (Vit A) through the blood to the target tissue.
- RBP synthesis depends on person’s Vit A status
Describe the possible pathways B-carotene once converted into all-trans retinal via 15,15’-DO enzyme?
- converted into all-trans retinol via retinol dehydrogenase
- esterified into RE
- follows the pathways of RE
- -converted into all-trans retinoic acid
What is the sole purpose of retinal? how does this occur? where does this occur?
-all trans retinol is converted to 11-cis retinal (in the eye)
- 11-cis retinal is converted to Rhodopsin
- When exposed to light,
Rhodopsin –> Opsin + all-trans retinal
- This phenomenon sends neural signals that induce VISION!
- Both opsin and all trans retinal are recycled in the Interphotoreceptor matrix
What are photoreceptor (Rod) cells and how do they absorb to light?
Photoreceptor (Rod) cells in the retina detect and convert light into neural signals that induce vision. They use Rhodopsin to absorb light.
What is the function of Retinoic acid?
- RA binds to and activates RAR (retinoic acid receptor)
- stimulated growth hormones
- creates a large combination of transcription factors
- good regulation of gene expression and differentiation of cells
What is a symptom of Vit A deficiency at the cellular level?
- poor cell differentiation
- keratinization, but no mucus secretion
- no mucus causes a weak epithelial layer that is susceptible to bacteria and viruses
What is keratin? What is keratinization? What are the causes and symptoms?
- A major protein expressed in the epithelial cells
- build of keratin in the epithelial cells that makes them tough and water-resistant
- lack of mucous
- caused by vit A deficiency (specifically RA deficiency)
What is the most severe consequence of vit A toxicity? What drug is known to cause vit A toxicity in pregnant women?
- liver cell death
- Vit A spills out and damages nearby liver cells
- Accutane has too much vit A (13-cis retinoic acid), known to cause birth defects in pregnant women
